How to Find the Area of a Polygon

A polygon is any flat shape that has straight lines for sides. Some common polygons are squares, parallelograms, triangles and rectangles. The area of an object is the amount of square units that are needed to fill a shape. To find the area of a shape, you simple have to measure the shape and plug those measurements into a mathematic formula.

Finding the Area of a Square

Make sure the shape is a true square by measuring all of the sides. If all of the sides are the same length, the shape is a square, not a rectangle.

Measure the length of one side of the square.

Multiply the length by itself. For example, if the length were 4 inches, multiply 4 by 4. The mathematical formula for a square is Area = SideÂ².

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Finding the Area of a Rectangle and Parallelogram

Measure one of the smaller sides, also known as the base, of the rectangle.

Measure one of the longer sides, also known as the height, of the rectangle.

Multiply the two measurements together to get the area of the polygon. The mathematical formula for a rectangle or a parallelogram is Area=Base X Height.

Finding the Area of Triangles

Measure the base of the triangle.

Measure the longest side, also known as the height, of the triangle.

Multiply the two measurements together to get the area of a quadrilateral, which is a triangle stacked upon itself.

Divide the answer by 2 to get the area of a triangle. The mathematic formula for a triangle is Area=Base (x) Height 1/2.

Tip

The area of a polygon is always a positive number.

References

About the Author

Since 1998 Alina McKee has written for dozens of traditional and online beauty, fashion, health and parenting publications including Pregnancy.org, Mama Health and Real Beauty. As a professional artist, her articles about these subjects have been used in magazines and websites around the globe. McKee has a diploma in fine art from Stratford Art School.